Ultraviolet/infrared absorbent green glass

ABSTRACT

Ultraviolet/infrared absorbent green glass is composed of soda-lime-silica glass including 0.001 to 2 wt. % Li 2 O and, as colorant, 0.4 to 2 wt. % total iron oxide expressed as Fe 2 O 3  (T-Fe 2 O 3 ) wherein FeO expressed as Fe 2 O 3  is 15 to 60% of T-Fe 2 O 3 . The glass has visible light transmittance (YA) of not less than 70%, measured by using the CIE illuminant A, and total solar radiation transmittance (TG) of not greater than 60%, when the glass has a thickness between 2.1 mm and 6 mm.

FIELD OF THE INVENTION

The present invention relates to a green glass which has advantages ofhigh heat ray absorptivity, high ultraviolet absorptivity, high quality,and high productivity. It particularly relates to a glass having highvisible light transmittance which has, a shade of green, and has a highheat ray absorption performance, and it more particularly relates to agreen glass which is suitable for a window glass to be reinforced andinstalled in a vehicle.

BACKGROUND OF THE INVENTION

A variety of glasses with ultraviolet/infrared absorptivity to be usedas a vehicle windshield have been proposed with the view of preventingdegradation of luxurious interior materials and reducing cooling load ofthe vehicle. In view of comfort of passengers and privacy protection, aglass having low visible light transmittance is preferably used for arear window glass of a vehicle.

The front windshield of a vehicle is obligated to have a visible lighttransmittance higher than a specific level for enough visibility of adriver. A glass having high visible light transmittance and providedwith ultraviolet and heat ray absorptivity has a greenish shade becausethe ends of its ultraviolet absorption range and infrared absorptionrange overlap the visible range.

Ultraviolet/infrared absorbent glasses having low to middle visiblelight transmittance, low ultraviolet transmittance and low total solarradiation transmittance have been disclosed in Japanese patentH10-114540A and H10-45425A. Since these ultraviolet/infrared absorbentglasses have high heat ray absorption characteristics, productivity ofeach glass in a glass melting furnace is low. Inside the meltingfurnace, a top of the glass is directly heated with flames, but thebottom of the glass material can not be sufficiently heated because alarge part of heat rays directed at the surface of the glass material bythe radiation of the flames are absorbed by the top of the glassmaterial. It is thus difficult to melt the glass material in the meltingfurnace uniformly.

The glass material is necessarily maintained at a higher-than-normaldegree of reduction in order to provide high heat ray absorptioncharacteristics thereto. Therefore, a large amount of reducing agents,mainly including graphite powder, etc., can be added into the glassbatch, but such agents are liable to cause unfused silica because theagents can exceedingly react with sulfate, mainly including sodiumsulfate, etc., which is added to the glass batch as a refining agent.

In order to melt the glass material uniformly, at least one of thefollowing processes can be adopted, such as: lowering the amount of theglass material below that for the ordinary operation; heating the bottomof the glass material by energizing electrodes inserted into the bottomof the furnace; and bubbling the glass material.

However, lowering the amount of the glass material below that for theordinary operation causes decrease of the production capacity, therebyraising the production cost. Electrical heating by insertion ofelectrodes in the bottom of the furnace and bubbling the glass materialrequire modification of the facilities. These processes can causedefects, such as: generation of a lot of defects such as bubbles in theglass depending upon the operating conditions, and result in significantdecline of the production capacity.

SUMMARY OF THE INVENTION

The low transmittance glass of the present invention is composed ofsoda-lime-silica glass comprising 0.001 to 2 wt. % Li₂O and, ascolorant, 0.7 to 2.2 wt. % total iron oxide (T-Fe₂O₃) expressed asFe₂O₃. The glass with a thickness between 2.1 mm and 6 mm has visiblelight transmittance (YA) of not greater than 65%, measured by using theCIE illuminant A, total solar radiation transmittance (TG) of notgreater than 60%, and ultraviolet transmittance (Tuv) defined by ISO9050 of not greater than 25%.

The low transmittance glass of the present invention has superior heatray absorption properties, and it is improved in quality andproductivity by including Li₂O in its base glass composition so as tolower viscosity of the glass material, accelerating melt andhomogenization of the glass material, and it also has superior capacityfor reinforcement.

Since the glass material of the low transmittance glass of the presentinvention has low viscosity, melt and homogenization of the glassmaterial are accelerated. The low transmittance glass is improved inquality and productivity, and is provided with low infraredtransmittance.

Since when applied with reinforcement by air blast cooling, the lowtransmittance glass of the present invention obtains higher surfacecompression than that of conventional ones, it is superior in capacityfor reinforcement. The low transmittance glass of the present inventionhas low visible light transmittance and low ultraviolet transmittance,so that it is suitable for a rear view window of a vehicle.

The ultraviolet/infrared absorbent green glass of the present inventionis composed of soda-lime-silica glass comprising 0.001 to 2 wt. % Li₂Oand, as colorant, 0.4 to 2 wt. % total iron oxide (T-Fe₂O₃) expressed asFe₂O₃ wherein FeO expressed as Fe₂O₃ is 15 to 60% of T-Fe₂O₃. The glasswith a thickness between 2.1 mm and 6 mm has visible light transmittance(YA) of not less than 70%, measured by using the CIE illuminant A, andtotal solar radiation transmittance (TG) of not greater than 60%.

The ultraviolet/infrared absorbent green glass of the present inventionhas superior heat ray absorption properties, and it is improved inquality and productivity by including Li₂O in its base glass compositionso as to lower viscosity of the glass material, accelerating melt andhomogenization of the glass material, and it also has superior capacityfor reinforcement.

Since the glass material of the low ultraviolet/infrared absorbent greenglass of the present invention has low viscosity, melt andhomogenization of the glass material are accelerated. The green glass isimproved in quality and productivity, and it is provided with lowinfrared transmittance. Since when applied with reinforcement by airblast cooling, the glass obtains higher surface compression than that ofconventional ones, it is superior in capacity for reinforcement. Thegreen glass has high visible light transmittance and low ultraviolettransmittance, so that it is suited for a window of a vehicle.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing a relationship between Li₂O content andtemperature at which log η becomes 2;

FIG. 2 is a graph showing a relationship between Li₂O content andsurface compression; and

FIG. 3 is a graph showing a relationship between Li₂O content andtransmittance of light having a wavelength of 700 nm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[Low Transmittance Glass]

A low transmittance glass of the present invention may be composed of abase glass composition comprising:

65 to 80 wt. % SiO₂;

0 to 5 wt. % Al₂O₃;

0 to 10 wt. % MgO;

5 to 15 wt. % CaO wherein a total amount of MgO and CaO is 5 to 15 wt.%;

10 to 20 wt. % Na₂O;

0 to 5 wt. % K₂O wherein a total amount of Na₂O and K₂O is 10 to 20 wt.%; and

0 to 5 wt. % B₂O₃.

The low transmittance glass of the present invention is preferable toinclude at least one selected from the group consisting of Se, CoO,Cr₂O₃, and NiO as colorant. The preferable content of Se is 0.0001 to0.1 wt. %, that of CoO is 0.0001 to 0.1 wt. %, that of Cr₂O₃ is 0.001 to2 wt. %, and that of NiO is 0.001 to 2 wt. %.

The low transmittance glass of the present invention is preferable toinclude at least one selected from the group consisting of TiO₂, CeO₂,MoO₃, V₂O₅ and La₂O₃ as colorant in an amount of 0.0001 to 1 wt %.

This low transmittance glass of the present invention has visible lighttransmittance (YA) of 5 to 65%, measured by using CIE illuminant A,total solar radiation transmittance (TG) of not greater than 50%, andultraviolet transmittance (Tuv) defined by ISO 9050 not greater than20%, in case that the glass has a thickness between 2.1 mm and 6 mm.

The description will be made as regard to the low transmittance glasscomposition of the present invention. It should be noted that content ofeach component will be represented with percentage by weight.

Li₂O is a component for lowering viscosity of the glass material andthus improving productivity of the glass. Since Li₂O has an effect ofmaking thermal expansion coefficient and Young's modulus of the glasslarger in case that the content of Li₂O is in a specific range, Li₂O isalso a component for increasing surface compression of the glass whenthe glass is applied with reinforcement by air blast cooling, improvinga capacity for reinforcement of the glass.

When the content of Li₂O is not greater than 2%, viscosity of the glassmaterial becomes lowered as the content of Li2O increases, and thusproductivity of the glass becomes improved. However, when the content ofLi₂O is greater than 2%, the effect of lowering viscosity decreases eventhough the content of Li₂O increases. When the content of Li₂O is lessthan 0.001%, Li₂O does not sufficiently give its effect of loweringviscosity to the glass material. The relationship between the content ofLi₂O and the temperature at which log η becomes 2 in a typicalsoda-lime-silica glass is shown in FIG. 1. It is noted that thetemperature at which log η becomes 2 decreases monotonously as thecontent of Li₂O increases, and the slope becomes gentle as the contentof Li₂O exceeds 2%. Therefore, the content of Li₂O is set in the 0.001to 2% range in the present invention. Since Li₂O material is costly, thecontent of Li₂O is preferably taken as less than 2% from a compromisebetween the cost and the effect of Li₂O.

When the content of Li₂O is not greater than 0.5%, surface compressionof the glass reinforced with air blast cooling increases as the contentof Li₂O increases. When the content of Li₂O is more than 0.5%, surfacecompression of the glass is approximately constant even though thecontent of Li₂O increases. The relationship between the content of Li₂Oand the surface compression in a typical soda-lime-silica glass is shownin FIG. 2. It is noted that although the surface compression increasesas the content of Li₂O increases, it becomes approximately constant asthe content of Li₂O exceeds 0.5%. The content of Li₂O is preferablytaken as 0.5% or less from a compromise between the cost and the effectof Li₂O. When the increase of surface compression of the glass byaddition of Li₂O is expected, Li₂O is preferably added in an amount of0.05% or more.

Iron oxide is present in the form of Fe₂O₃ and the form of FeO in theglass. Fe₂O₃ is a component for improving the ultraviolet absorptivityand FeO is a component for improving the infrared absorptivity. When thetotal amount of iron oxide (T-Fe₂O₃) expressed as Fe₂O₃ is less than0.7%, the efficiency of ultraviolet and infrared absorptivity becomessmall so as not to provide desired optical properties. On the otherhand, when T-Fe₂O₃ exceeds 2.2%, the infrared absorptivity of T-Fe₂O₃becomes too high to produce the glass in an ordinary melting furnace,and the color unpreferably becomes too greenish. In case of successivelyproducing glasses by a glass melting furnace with a large amount ofT-Fe₂O₃, long time is required to change the glass composition in thefurnace.

In the present invention, an effect of shifting the light absorptionpeak of FeO toward the short wavelength range of light is given bycoexistence of FeO and Li₂O in the soda lime glass. In order toillustrate this effect, the relationship between the content of Li₂O andthe transmittance of light having a wavelength of 700 nm is shown inFIG. 3. It is noted that the transmittance of light having a wavelengthof 700 nm decreases according as the content of Li₂O increases. Additionof Li₂O makes it possible to lower visible light transmittanceeffectively with a small content of FeO.

When the FeO/T-Fe₂O₃ ratio (a weight of FeO expressed as Fe₂O₃ againstT-Fe₂O₃) is less than 20%, sufficient heat ray absorptivity can not beobtained. When FeO/T-Fe₂O₃ ratio is more than 50%, silica-rich ream andsilica scum are present in a glass because the glass is highly reduced,resulting in decrease of productivity.

SiO₂ is a main component for forming skeleton of glass. Less than 65%SiO₂ lowers the durability of the glass and more than 80% SiO₂ raisesthe melting temperature of the glass so high.

Al₂O₃ is a component for improving the durability of the glass. Morethan 5% Al₂O₃ raises the melting temperature of the glass so high.

MgO and CaO improve the durability of the glass and adjust a liquidustemperature and viscosity of the glass. More than 10% MgO raises theliquidus temperature. Less than 5% or more than 15% CaO raises theliquidus temperature of the glass. The durability of the glass islowered when the total amount of MgO and CaO is less than 5%, while theliquidus temperature is increased when the total exceeds 15%.

Na₂O and K₂O prompt the glass to melt. The efficiency of promotion ofmelting becomes poor when Na₂O is less than 10% or the total of Na₂O andK₂O is less than 10%, while the durability of the glass is lowered whenNa₂O exceeds 20% or the total of Na₂O and KO exceeds 20%. K₂O ispreferable not to exceed 5% because of its expensive cost.

B₂O₃ is a component for improving the durability of the glass, promptingto melt, and yet enhancing the ultraviolet absorption. B₂O₃ should beless than 5%, since difficulties during molding are caused due to thevaporization of B₂O₃ when B₂O₃ exceeds 5%.

Se, CoO, Cr₂O₃ and NiO are components for adjusting visible lighttransmittance and color of the glass, so that it is preferable to add atleast one of these components in the glass.

Se gives a red to pink shade to the glass and also gives grayish shadeto the glass by cooperating with FeO or CoO. When Se is included in theglass, more than 0.1% Se reduces visible light transmittance too much,so that the glass can not be provided with desired properties. Thepreferable content of Se is 0.0001 to 0.1%.

CoO gives a blue shade to the glass and also gives grayish shade to theglass by cooperating with Se, NiO or Fe₂O₃. When CoO is included in theglass, more than 0.1% CoO reduces visible light transmittance too much,so that the glass can not be provided with desired properties. Thepreferable content of CoO is 0.0001 to 0.1%.

Cr₂O₃ gives a green shade to the glass and also adjusts visible lighttransmittance and color of the glass by cooperating with Se, NiO, CoO orFe₂O₃. More than 2% CrO₃ reduces visible light transmittance too much,so that the glass can not be provided with desired properties. Thepreferable content of Cr₂O₃ is 0.001 to 2%.

NiO gives a brown to purple shade to the glass and also gives grayishshade to the glass by cooperating with FeO or CoO. More than 2% NiOreduces visible light transmittance too much, so that the glass can notbe provided with desired optical properties, and it unpreferablyactivates formation of nickel sulfide stones. The preferable content ofNiO is 0.001 to 2%.

In order to obtain more desirable shade and properties, at least oneselected from the group consisting of TiO₂, CeO₂, MoO₃, V₂O₅ and La₂O₃may be added as auxiliary ultraviolet absorbing agent in an amount of0.0001 to 1%.

Sulfate of alkaline or alkaline earth metal has been added as a refiningagent for the glass, and the glass usually includes SO₃ in an amount ofabout 0.1 to 0.5%. One or more than two among Sb₂O₃, SnO₂, and the likemay be added as a reducing agent or a refining agent for the glass in anamount not greater than 1%. In order further securely to prevent theformation of nickel sulfide stones, ZnO may be added in an amount notgreater than 1%.

The low transmittance glass of the present invention has visible lighttransmittance (YA) of not greater than 65%, measured by using the CIEilluminant A, total solar radiation transmittance (TG) of not greaterthan 60%, and ultraviolet transmittance (Tuv) defined by ISO 9050 of notgreater than 25%, when the glass has a thickness in a range of 2.1 to 6mm. YA is preferable to be in a range of 5 to 65%, TG is preferable notto exceed 50%, and Tuv is preferable not to exceed 20%.

Hereinafter, examples and comparative examples of the low transmittanceglass of the present invention will be described.

EXAMPLES 1-10

The formulation of typical soda-lime-silica glass material is shown inTable 1. Lithium oxide, ferric oxide, metallic selenium, cobalt oxide,chromium oxide, nickel oxide, titanium oxide, cerium oxide, molybdenumoxide, vanadium pentoxide and lanthanum oxide were added to the glassmaterial as desired. The glass material thus prepared was held in anelectric furnace at 1500° C., for 4 hours. The molten glass was cast ona stainless plate and held at 650° C., for 1 hour, and then annealed tothe room temperature in the furnace so as to obtain 6 mm thick glassplates.

TABLE 1 component content [g] silica sand 973.6 dolomite 255.7 limestone30.24 soda ash 230.02 salt cake 9.881 carbon 0.617 total 1500

The obtained glass plates were polished, so that each glass plate has athickness between 3.5 mm and 5 mm, so as to obtain the samples. Eachsample was determined in optical properties including visible lighttransmittance (YA) measured by using the CIE illuminant A, total solarradiation transmittance (TG), ultraviolet transmittance (Tuv) defined byISO 9050, dominant wavelength (DW) and excitation purity (Pe) measuredby using the CIE illuminant C.

The samples were also determined in physical properties including glasstransition temperature (Tg), deformation temperature (Td), mean thermalexpansion coefficient of the 50 to 350° C. range (α₍₅₀₋₃₅₀₎), Young'smodulus (E), surface compression and the temperature at which log ηbecomes 2. Each sample was formed into a rod-like shape having a lengthof 15 mm and a diameter of 5 mm, and then it was loaded with a load of 5g and heated from the room temperature to 700° C. at a rate of 10° C.per minutes with silica glass rod prepared as a standard sample by theuse of EXSTAR 6000 (SEIKO Electronics Inc.), so as to measure glasstransition temperature (Tg), deformation temperature (Td) and meanthermal expansion coefficient of the 50 to 350° C. range (α₍₅₀₋₃₅₀₎).Young's modulus (E) was measured with ultrasonic wave according tosing-around method, surface compression was measured with aBabinet-Style surface stress meter according to via-scope method, andthe temperature at which log η becomes 2 was measured according toplatinum ball drawing method.

The base glass composition, the content of colorant, FeO/T-Fe₂O₃ ratio,the optical properties and the physical properties of each sample wereshown in Tables 2 and 3. The contents of the components in these tablesare indicated as percentage by weight.

TABLE 2 Example 1 Example 2 Example 3 Example 4 Example 5 glasscomposition [wt. %] SiO₂ 71.0 71.5 70.7 71.4 71.2 Al₂O₃ 1.40 0.11 0.891.35 1.35 MgO 3.64 3.75 4.13 3.68 3.68 CaO 7.66 8.62 8.38 7.75 7.74 Na₂O13.7 13.6 13.2 13.7 13.6 K₂O 0.91 0.07 0.23 0.77 0.76 Li₂O 1.00 2.000.50 0.05 0.12 T-Fe₂O₃ 1.25 1.40 1.42 1.30 1.30 FeO/T-Fe₂O₃ 0.23 0.240.22 0.23 0.23 NiO 0.065 — — 0.016 0.098 CoO 0.019 0.022 0.012 0.0040.020 Se 0.001 0.003 0.0005 — — Cr₂O₃ — — 0.002 — — TiO₂ 0.02 0.03 0.030.03 0.03 optical properties thickness [mm] 5 4 4 4 4 YA [%] 17.2 16.337.8 48.6 16.9 TG [%] 17.0 13.7 27.5 27.0 15.4 Tuv [%] 9.0 2.4 4.7 8.78.2 DW [nm] 556 522 494 502 521 Pe [%] 9.0 1.0 5.8 5.0 4.5 physicalproperties Tg [° C.] 531.6 499.1 531.9 547.1 544.8 Td [° C.] 603.2 557.7602.7 625.4 623.7 α₍₅₀₋₃₅₀₎ × e⁻⁷ 93.4 92.6 95.8 90.0 94.4 E [GPa] 76.277.3 74.3 74.0 75.0 surface compressive stress [MPa] 112.0 112.8 112.0109.0 111.3 temperature at which log η becomes 2 [° C.] 1397 1387 14191430 1431

TABLE 3 Example 6 Example 7 Example 8 Example 9 Example 10 glasscomposition [wt. %] SiO₂ 71.4 71.2 71.6 72.0 71.6 Al₂O₃ 1.35 1.35 1.351.35 1.34 MgO 3.69 3.68 3.70 3.72 3.70 CaO 7.76 7.74 7.78 7.83 7.78 Na₂O13.3 13.3 12.4 11.4 11.3 K₂O 0.77 0.76 0.77 0.77 0.77 Li₂O 0.33 0.331.01 1.50 2.00 T-Fe₂O₃ 1.30 1.30 1.31 1.31 1.31 FeO/T-Fe₂O₃ 0.24 0.220.22 0.22 0.22 NiO 0.016 0.098 0.098 0.099 0.099 CoO 0.004 0.020 0.0200.020 0.020 Se — — — — — Cr₂O₃ — — — — — TiO₂ 0.03 0.03 0.03 0.03 0.03optical properties thickness [mm] 4 3.5 3.5 3.5 3.5 YA [%] 49.8 20.820.7 20.6 20.6 TG [%] 27.9 19.3 19.1 19.1 19.0 Tuv [%] 9.8 10.3 10.1 9.89.8 DW [nm] 502 525 524 523 524 Pe [%] 5.0 4.3 4.3 4.4 4.2 physicalproperties Tg [° C.] 535.5 539.2 518.6 510.2 504.7 Td [° C.] 612.2 615.4596.8 598.1 586.2 α₍₅₀₋₃₅₀₎ × e⁻⁷ 95.1 96.5 91.2 90.2 93.8 E [GPa] 74.975.0 76.3 77.5 78.5 surface compressive stress [MPa] 112.1 114.3 109 110117 temperature at which log η becomes 2 [° C.] 1417 1429 1429 1396 1390

It is apparent from Tables 2, 3 that each glass of the present inventionhas the temperature at which log η becomes 2, which is an index ofhigh-temperature viscosity, so that the low transmittance glass of thepresent invention is excellent in meltability. Each low transmittanceglass of the invention has also high surface compression, so that thelow transmittance glass has large capacity for reinforcement.

Examples 1-10 have preferable optical properties, such as: visible lighttransmittance (YA) measured by using the CIE illuminant A of 5 to 65%,total solar radiation transmittance (TG) of not greater than 50% andultraviolet transmittance (Tuv) defined by ISO 9050 of not greater than20%. These examples also have dominant wavelength (DW) measured by usingthe CIE illuminant C of 490 to 560 nm and excitation purity (Pe)measured by using the CIE illuminant C of not greater than 9%.

COMPARATIVE EXAMPLES 1 AND 2

The glass composition, the optical properties and the physicalproperties of Comparative Examples 1 and 2 each of which was prepared inthe same way as Examples 1-10 except for the glass composition are shownin Table 4.

TABLE 4 Comparative Comparative Example 1 Example 2 glass composition[wt. %] SiO₂ 70.5 70.6 Al₂O₃ 1.66 1.66 MgO 3.72 3.70 CaO 7.96 7.86 Na₂O13.9 13.7 K₂O 0.79 0.81 Li₂O 0.00 0.00 T-Fe₂O₃ 1.26 1.29 FeO/T-Fe₂O₃0.27 0.23 NiO 0.016 0.064 CoO 0.005 0.018 Se — — Cr₂O₃ — — TiO₂ 0.030.03 optical properties thickness [mm] 5.0 4.0 YA [%] 39.9 23.3 TG [%]21.7 18.7 Tuv [%] 5.8 8.1 DW [nm] 502 496 Pe [%] 5.9 7.1 physicalproperties Tg [° C.] 558.5 557.3 Td [° C.] 643.5 642.3 α₍₅₀₋₃₅₀₎ × e⁻⁷92.6 92.6 E [ GPa] 74.2 74.2 surface compressive stress [ MPa] 106.0107.3 temperature at which log η becomes 2 [° C.] 1436 1434

Comparative Examples 1 and 2 are conventional low transmittance glasseswhich do not include Li₂O. These glasses have higher temperature atwhich log η becomes 2 and lower surface compression than those of thepresent invention, resulting in reduction of productivity and capacityfor reinforcement.

As described above, the present invention provides a low transmittanceglass composition having superior heat ray absorption characteristicsand an advantage of high productivity. Particularly, the presentinvention provides a glass having low visible light transmittance whichhas smoky color, such as gray to green, and high heat ray absorptioncharacteristics, more particularly, it provides a low transmittanceglass which is suited for a window glass to be reinforced and installedin a vehicle.

[Ultraviolet/Infrared Absorbent Green Glass]

The ultraviolet/infrared absorbent green glass of the present inventionpreferably has the same base glass composition as the low transmittanceglass mentioned above.

The ultraviolet/infrared absorbent green glass of the present inventionpreferably includes as colorant:

0.4 to 1 wt. % total iron oxide expressed as Fe₂O₃ (T-Fe₂O₃);

0 to 1 wt. % TiO₂; and

0 to 2 wt. % Ceo₂.

The ultraviolet/infrared absorbent green glass preferably hasultraviolet transmittance (Tuv) defined by ISO 9050 of not greater than35%, dominant wavelength (DW) measured by using the CIE illuminant C of490 to 560 nm, and excitation purity (Pe) measured by using the CIEilluminant C of less than 6% when the glass has a thickness between 2.1mm and 6 mm.

The ultraviolet/infrared absorbent green glass is preferable to includeat least one selected from the group consisting of Se, CoO, Cr₂O₃,Mn₂O₃, CuO, Nd₂O₃, Er₂O₃, MoO₃, V₂O₅ and La₂O₃ in an amount of 0.0001 to0.1 wt. %.

The description will be made as regard to the ultraviolet/infraredabsorbent green glass composition of the present invention. It should benoted that content of each component will be represented with percentageby weight.

The description of the reason why the above base glass composition isdesirable for the low transmittance glass applies equally to that forthe ultraviolet/infrared absorbent green glass.

The description will be made as regard to the colorant of theultraviolet/infrared absorbent green glass of the present invention.

Iron oxide is present in the form of Fe₂O₃ and the form of FeO in theglass. Fe₂O₃ is a component for improving the ultraviolet absorptivityand FeO is a component for improving the infrared absorptivity. When thetotal amount of iron oxide (T-Fe₂O₃) expressed as Fe₂O₃ is less than0.4%, the efficiency of ultraviolet and infrared absorptivity becomessmall so as not to provide desired optical properties. On the otherhand, when T-Fe₂O₃ exceeds 2%, visible light transmittance becomes toolow and the color of the glass unpreferably becomes too greenish. WhenTiO₂ and CeO₂ also are included in the glass, the content of T-Fe₂O₃ ispreferable not to be greater than 1%.

When the FeO/T-Fe₂O₃ ratio (a weight of FeO expressed as Fe₂O₃ againstT-Fe₂O₃) is less than 15%, sufficient heat ray absorptivity can not beobtained. If FeO/T-Fe₂O₃ ratio is more than 60%, silica-rich ream andsilica scum are present, in a glass because the glass is highly reduced,unpreferably resulting in decrease of productivity and lapse of theeffect of Li₂O. The FeO/T-Fe2O₃ ratio is preferable not to be greaterthan 50%, more preferable not to be greater than 35%.

TiO₂ is a component for improving the ultraviolet absorptivityparticularly by interaction with FeO. The content of TiO₂ is preferablenot to be greater than 1%. More than 1% TiO₂ unpreferably raises costand makes the shade of the glass yellowish. When the effect of absorbingultraviolet of TiO₂ is expected, TiO₂ is preferably added in an amountof 0.01% or more.

CeO₂ is a component for improving the ultraviolet absorptivity and ispresent in the form of Ce³⁺ or in the form of Ce⁴⁺ in the glass.Particularly, Ce³⁺ is effective in absorbing ultraviolet with lessabsorptivity in the visible range. The content of CeO₂ is preferable notto be greater than 2%. More than 2% CeO₂ unpreferably raises cost andreduces visible light transmittance. When the effect of absorbingultraviolet of CeO₂ is expected, CeO₂ is preferably added in an amountof 0.01% or more.

In order to obtain more desirable shade and optical properties, at leastone selected from the group consisting of Se, CoO, Cr₂O₃, Mn₂O₃, CuO,Nd₂O₃ and Er₂O₃ as colorant and the group consisting of MoO₃, V₂O₅ andLa₂O₃ as auxiliary ultraviolet absorbing agent may be added in an amountof 0.0001 to 1%.

Sulfate of alkaline or alkaline earth metal has been added as a refiningagent for the glass, and the glass usually includes SO₃ in an amount ofabout 0.1 to 0.5%. One or more than two among Sb₂O₃, SnO₂, and the likemay be added as a reducing agent or a refining agent for the glass in anamount not greater than 1%. In order further securely to prevent theformation of nickel sulfide stones, ZnO may be added in an amount notgreater than 1%.

The ultraviolet/infrared absorbent green glass of the present inventionis preferable to have visible light transmittance (YA) of not less than70%, measured by using the CIE illuminant A, and total solar radiationtransmittance (TG) of not greater than 60% when the glass has athickness between 2.1 mm and 6 mm.

The ultraviolet/infrared absorbent green glass of the present inventionhas ultraviolet transmittance (Tuv) defined by ISO 9050 of not greaterthan 35%, dominant wavelength (DW) measured by using the CIE illuminantC of 490 to 560 nm, and excitation purity (Pe) measured by using the CIEilluminant C of less than 6%.

Hereinafter, examples and comparative examples of theultraviolet/infrared absorbent green glass of the present invention willbe described.

EXAMPLES 11-22

Lithium oxide, ferric oxide, titanium oxide, cerium oxide, metallicselenium, cobalt oxide, nickel oxide, chromium oxide, manganese oxide,copper oxide, neodymium oxide, erbium oxide, molybdenum oxide, vanadiumpentoxide, lanthanum oxide and carbon based reducing agent, includingcarbon powder, etc., were added to the typical soda lime silica glassbatch material as desired. The glass material thus prepared was held inan electric furnace at 1500° C., for 4 hours. The molten glass was caston a stainless plate, and then annealed to the room temperature so as toobtain 6 mm thick glass plates.

The obtained glass plates were polished, so that each glass plate has athickness between 2.6 mm and 5 mm, so as to obtain the samples. Eachsample was determined in optical properties including visible lighttransmittance (YA) measured by using the CIE illuminant A, total solarradiation transmittance (TG), ultraviolet transmittance (Tuv) defined byISO 9050, dominant wavelength (DW) and excitation purity (Pe) measuredby using the CIE illuminant C.

The samples were also determined in physical properties including glasstransition temperature (Tg), deformation temperature (Td), mean thermalexpansion coefficient of the 50 to 350° C. range (α₍₅₀₋₃₅₀₎), Young'smodulus (E), surface compression and the temperature at which log ηbecomes 2. Each sample was formed into a rod-like shape having a lengthof 15 mm and a diameter of 5 mm, and then it was loaded with a load of 5g and heated from the room temperature to 700° C. at a rate of 10° C.per minutes with silica glass rod prepared as a standard sample by theuse of EXSTAR 6000 (SEIKO Electronics Inc.), so as to measure glasstransition temperature (Tg), deformation temperature (Td) and meanthermal expansion coefficient of the 50 to 350° C. range (α₍₅₀₋₃₅₀₎).Young's modulus (E) was measured with ultrasonic wave according tosing-around method, surface compression was measured with aBabinet-Style surface stress meter according to via-scope method, andthe temperature at which log η becomes 2 was measured according toplatinum ball drawing method.

The glass composition and FeO/T-Fe₂O₃ ratio of each sample were shown inTables 5 and 6. The contents of the components in these tables areindicated as percentage by weight. Tables 5 and 6 also show the opticalproperties and the physical properties of each sample.

TABLE 5 Example 11 Example 12 Example 13 Example 14 Example 15 Example16 glass composition [wt. %] SiO₂ 70.8 70.9 69.5 69.5 68.2 68.3 Al₂O₃1.74 1.88 1.71 1.91 2.87 2.87 MgO 4.09 4.02 3.19 3.11 1.64 1.65 CaO 7.947.96 8.26 8.44 9.21 9.22 Na₂O 13.8 13.6 14.5 14.4 15.0 14.8 K₂O 0.800.96 0.23 0.07 0.92 0.92 Li₂O 0.05 0.09 0.06 0.12 0.16 0.33 T-Fe₂O₃ 0.510.55 0.63 0.65 0.64 0.64 FeO/T-Fe₂O₃ 0.23 0.24 0.32 0.31 0.22 0.18 TiO₂— — 0.09 0.14 0.16 0.16 CeO₂ — — 1.65 1.65 1.17 1.17 optical propertiesthickness [mm] 5.0 3.5 4.0 3.4 3.1 3.1 YA [%] 78.5 80.3 72.9 75.3 77.077.5 TG [%] 54.9 59.7 45.5 49.5 49.6 50.7 Tuv [%] 24.5 32.4 8.6 10.115.0 15.3 DW [nm] 500 500 508 510 497 498 Pe [%] 2.4 1.9 2.6 2.2 3.1 2.9physical properties Tg [° C.] 557.3 555.3 556.2 552.3 544.0 537.6 Td [°C.] 626.8 623.0 629.9 627.9 624.3 618.1 α₍₅₀₋₃₅₀₎ × e⁻⁷ 92.9 93.1 94.393.9 100.8 101.8 E [GPa] 75.40 75.60 75.14 75.47 75.10 75.37 surfacecompressive stress [MPa] 109.9 110.5 111.4 111.4 120.8 122.7 temperatureat which log η becomes 2 [° C.] 1384 1381 1384 1383 1383 1380

TABLE 6 Example 17 Example 18 Example 19 Example 20 Example 21 glasscomposition [wt. %] SiO₂ 68.3 67.9 70.0 69.0 69.5 Al₂O₃ 2.87 2.85 1.702.40 1.90 MgO 1.65 1.64 2.70 1.70 1.70 CaO 9.23 9.16 8.04 9.11 9.00 Na₂O14.5 14.7 13.5 13.4 14.1 K₂O 0.92 0.92 0.75 0.75 0.80 Li₂O 0.50 0.331.50 2.00 1.00 T-Fe₂O₃ 0.64 0.78 0.80 0.88 0.80 FeO/T-Fe₂O₃ 0.18 0.270.26 0.24 0.24 TiO₂ 0.16 0.29 0.06 0.10 0.06 CeO₂ 1.17 1.44 0.65 0.600.87 optical properties thickness [mm] 3.1 2.6 2.6 2.6 2.6 YA [%] 77.275.0 75.7 74.9 76.5 TG [%] 50.1 47.0 47.6 43.9 49.6 Tuv [%] 15.3 12.715.6 11.8 15.0 DW [nm] 498 503 499 515 508 Pe [%] 3.0 2.6 2.6 2.7 2.4physical properties Tg [° C.] 530.2 535.4 517.4 501.0 511.7 Td [° C.]605.1 611.6 585.2 562.8 575.9 α₍₅₀₋₃₅₀₎ × e⁻⁷ 101.6 100.6 101.6 101.7101.7 E [GPa] 75.86 75.30 78.50 78.20 76.00 surface compressive stress[MPa] 123.4 120.8 123.6 123.1 123.8 temperature at which log η becomes 2[° C.] 1380 1381 1378 1377 1378

It is apparent from Tables 5, 6 that each glass of the present inventionhas the temperature at which log η becomes 2, which is an index ofhigh-temperature viscosity, so that the ultraviolet/infrared absorbentgreen glass of the present invention is excellent in meltability. Eachultraviolet/infrared absorbent green glass of the invention has alsohigh surface compression, so that the ultraviolet/infrared absorbentgreen glass has large capacity for reinforcement.

Examples 11-21 have preferable optical properties, such as: ultraviolettransmittance (Tuv) defined by ISO 9050 of not greater than 35%,dominant wavelength (DW) measured by using the CIE illuminant C of 490to 560 nm and excitation purity (Pe) measured by using the CIEilluminant C of smaller than 6% when each glass has a thickness between2.1 mm to 6 mm.

Examples 13-22 have more preferable optical properties to Examples 11and 12 because ultraviolet transmittance (Tuv) of Examples 13-22 islower than that of Examples 11 and 12.

COMPARATIVE EXAMPLES 3 AND 4

The glass composition, the optical properties and the physicalproperties of Comparative Examples 3 and 4 each of which was prepared inthe same way as Examples 11-21 except for the glass composition areshown in Table 7.

TABLE 7 Comparative Comparative Example 3 Example 4 glass composition[wt. %] SiO₂ 71.3 69.9 Al₂O₃ 1.55 1.48 MgO 4.02 3.13 CaO 7.99 8.49 Na₂O13.7 14.5 K₂O 0.97 0.07 Li₂O 0.00 0.00 T-Fe₂O₃ 0.52 0.65 FeO/T-Fe₂O₃0.22 0.31 TiO₂ — 0.14 CeO₂ — 1.65 optical properties thickness [ mm] 3.43.4 YA [ %] 82.9 75.4 TG [ %] 63.9 49.7 Tuv [ %] 32.2 10.0 DW [ nm] 500510 Pe [ %] 1.7 2.2 physical properties Tg [° C.] 555.5 552.7 Td [° C.]624.5 628.1 α₍₅₀₋₃₅₀₎ × e⁻⁷ 92.7 93.6 E [ GPa] 74.59 74.40 surfacecompressive stress [ MPa] 108.1 109.1 temperature at which log η becomes2 [° C.] 1410 1387

Comparative Examples 3 and 4 are conventional ultraviolet/infraredabsorbent glasses which do not include Li₂O. These glasses have highertemperature at which log η becomes 2 and lower surface compression thanthose of the present invention, resulting in reduction of productivityand capacity for reinforcement.

As described above, the present invention makes it possible to producean ultraviolet/infrared absorbent glass having high visible lighttransmittance and greenish shade at lower cost than that of conventionalones, because the present invention reduces viscosity of the glass athigh temperature. Particularly, the ultraviolet/infrared absorbent greenglass of the present invention exhibits superior capacity forreinforcement, so that it is especially fitted for a window glass of avehicle.

What is claimed is:
 1. Ultraviolet/infrared absorbent green glassconsisting essentially of base glass composition and colorant, said baseglass composition consisting essentially of: 65 to 80 wt. % SiO₂; 0.001to 2 wt. % of Li₂O; 0 to 5 wt. % Al₂O₃; 0 to 10 wt. % MgO; 5 to 15 wt. %CaO wherein a total amount of MgO and CaO is 5 to 15 wt. %; 10 to 20 wt.% Na₂O; 0 to 5 wt. % K₂O wherein a total amount of Na₂O and K₂O is 10 to20 wt. %; and 0 to 5 wt. % B₂O₃, and said colorant including: 0.4 to 1wt. % total iron oxide expressed as Fe₂O₃ (T-Fe₂O₃), wherein FeOexpressed as Fe₂O₃ is 15 to 60% of T-Fe₂O₃; 0 to 1 wt. % Ti₂O; and 0 to2 wt. % CeO₂, wherein said glass has visible light transmittance (YA) ofnot less than 70%, measured by using CIE illuminant A, and total solarradiation transmittance (TG) of not greater than 60%, when said glasshas a thickness between 2.1 mm and 6 mm.
 2. Ultraviolet/infraredabsorbent green glass as claimed in claim 1, wherein Li₂O is containedin an amount of less than 2 wt. %.
 3. Ultraviolet/infrared absorbentgreen glass as claimed in claim 1, wherein Li₂O is contained in anamount of 0.05 to 0.5 wt. %.
 4. Ultraviolet/infrared absorbent greenglass as claimed in claim 1, wherein said ultraviolet/infrared absorbentgreen glass includes: 0.01 to 1 wt. % Ti₂O; and 0.01 to 2 wt. % CeO₂. 5.Ultraviolet/infrared absorbent green glass as claimed in claim 1,wherein said ultraviolet/infrared absorbent green glass has ultraviolettransmittance (Tuv) defined by ISO 9050 of not greater than 35%,dominant wavelength (DW) measured by using CIE illuminant C of 490 to560 nm, and excitation purity (Pe) measured by using the CIE illuminantC of less than 6%, when said glass has a thickness between 2.1 mm and 6mm.
 6. Ultraviolet/infrared absorbent green glass as claimed in claim 1,wherein said colorant further includes at least one material selectedfrom the group consisting of Se, CoO, Cr₂O₃, Mn₂O₃, CuO, Nd₂O₃, Er₂O₃,MoO₃, V₂O₅ and La₂O₃ in an amount of 0.0001 to 0.1 wt %. 7.Ultraviolet/infrared absorbent green glass as claimed in claim 1,wherein said glass has surface compression of more than 109.9 MPa aftertempering.
 8. Ultraviolet/infrared absorbent green glass as claimed inclaim 1, wherein said glass has surface compression of between 109.9 MPaand 123.8 MPa after tempering.
 9. Ultraviolet/infrared absorbent greenglass as claimed in claim 4, wherein said colorant of the glass consistsessentially of 0.4 to 1 wt. % total iron oxide, 0.01 to 1 wt. % Ti₂O,and 0.01 to 2 wt. % CeO₂.